Indoor environments present a number of challenges for wireless communications network deployment. Because of object clutter and the walls and ceilings of the rooms in an indoor environment, signal reflections off these surfaces present a complex multipath propagation environment for wireless signals. Because people move around within these environments, this also affects the propagation environment in a highly dynamic manner, making adequate signal reception challenging.
One way in which this problem is addressed is with the use of diverse antennas which are spaced apart from each other to receive different signal components of the originally transmitted signal. Either the best signal component is selected or some combination of the signal components from each antenna is generated to give an improved received signal. However the signal combination is not straightforward and is complicated by the delay spread introduced by unequal cable lengths to the different antennas. In a highly dynamic propagation environment such as inside a room, the selection or combination process is constantly having to update based on these changing conditions which requires a high processing load. Such diversity antenna approaches are shown in EP869630, and “Performance Advantages of Distributed Antennas in Indoor Wireless Communication Systems”, IEEE Vehicular Technology Conference, volume 3, pp 1522-1526, Jun. 1994.
Another method of addressing the problems of this type of environment is by using terminals within the environment as repeaters which relay transmission signals between each other and an access point antenna to provide a series of line of sight (LOS) signal propagation paths between a particular terminal and the access point antenna. Such a system is described in “Link Capacity Analysis for Virtual Antenna Arrays” by Mischa Dohler, Jose Dominguez, Hamid Aghvami in IEEEE Vehicular Technology Conference, Fall 2002 IEEEE 56th, volume 1, pp 440-443, 2002. However, this sort of technique is highly dependent on the availability of mobile devices in the working proximity and as such the link quality is not always guaranteed as the mobile devices come and go.